1. Field of the Invention
The field of the invention relates to apparatus employing thermal energy for the production of work, power and the like, and, more particularly, to such apparatus adapted for recovering thermal energy from hot fluids, the sun, etc.
2. Description of the Prior Art
Large amounts of energy in the form of heat are wasted in many heat producing operations. For example, a steam-electric generating plant may waste much of the heat generated in the condensation of steam back into water for the boilers and much of the heat generated in nuclear reactor power plants is usually lost to the cooling water used to maintain the reactors at a safe operating temperature. Not only is the energy associated with such heat lost when the heat is dissipated into the air or when heated cooling water is discharged into rivers, etc, but the resulting thermal pollution is often a substantial problem and the subject of much environmental concern.
Often the thermal energy desired to be recovered is of relatively low quality because it is in the form of water (or other fluid) at a temperature less than the boiling point of water. Conventional means alone are, therefore, generally not adaptable for recovery of the thermal energy. In an attempt to recover some of the thermal energy contained in waste hot water, Sautter (U.S. Pat. No. 924,838) discloses apparatus for using part of the heat energy in the water to convert portions of the hot water into steam used to operate a steam turbine.
Substantial disadvantages are, however, associated with the use of steam systems: High pressure vessels must be provided to contain the steam and the materials used in components of the system must also be capable of withstanding high steam temperatures. Therefore, to construct and maintain such steam systems is comparatively expensive and may not be economically feasible. Similar problems are also associated with proposals for utilizing solar energy to convert, by means of reflectors, condensers, etc., water into steam and using the steam to drive steam turbines and generate electricity.
As a consequence, it is often preferable and economically more feasible to employ lower temperatures and pressures in non-steam operated thermal energy recovery apparatus, which may be constructed from comparatively inexpensive materials. This may be particularly the case when the temperature of the source fluid is low compared to steam temperatures and in applications requiring minimum attendance and maintenance.